Base for electric lamp or similar device



Nov. 11,1941. D. K. WRIGHT 2,262,629

I BASE FOR ELECTRIC LAMP OR SIMILAR DEVICE Filed Feb. 14', 1940 Fi.l. 2

Inventor: a ieL Kwrigh't,

His Aha-ne Patented Nov. 11, 1941 BASE FOR ELECTRIC LAMP OR SIMILAR DEVICE Daniel K. Wright, Cleveland Heights, Ohio, assignor to General Electric Company, a corporation or New York Application February 14, 1940, Serial No. 318,885

4 Claims.

My invention relates to electric incandescent lamps and similar devices comprising a bulb having an electrical energy translation element sealed therein and a base mounted on said bulb. More particularly, my invention relates to the terminal structure for such devices, including the base and the seal structure for the current leads to the filament or other light source. This application is a continuation-in-part of my application Serial No. 250,765, filed January 13,

One of the objects of my invention is to provide a lamp or similar device in which the usual re-entrant stem tube carrying the lead-in wires is eliminated and the seal or terminal portion of the device is so constructed as to permit the use in combination therewith of a base which may be inserted in ordinary sockets. I

For certain definite reasons it is desirable to employ, for high-intensity lamps, a mechanical base in which a firm connection between the lamp bulb and the base is maintained at all times, although in cases where the base portion a constructions are impractical and have proven unsatisfactory. The reason for this is that the bases were applied to conventional blown glass bulbs having relatively thin walls. These thin glass walls cannot readily withstand the pressure exerted thereon by the base deforming tool during the spinning of the base metal into the bulb neck depressions, with the result that they i requently cracked. Nor can such thin glass walls withstand the tremendous pressures exerted thereon by the base during the heating up and cooling down of the lamp, and resulting from the difference in the rates of expansion and contraction of the bulb glass and the surrounding base metal. Consequently, a slight clearance has to be provided between the base shell and the bulb neck to reduce these pressures to a minimum so as to efiectively prevent cracking of the bulb glass. But in doing so, a loose and wabbly base is very likely to result.

To provide a practical mechanical base struction which will not result in fracture or the bulb glass and'which will not become loose or wabbly 0n the bulb neck, I have found it necessary to employ a bulb neck of pressed glass having relatively thick walls, and to secure the base on the bulb neck by a relatively tight press fit. Such thick glass walls will readily withstand, without cracking, the pressures exerted thereon during the spinning of the base metal into the depressions in such walls, as'well as the pressures exerted by the base during the heating up and cooling down of the lamp. Furthermore, the relatively tight press fit between the base and the bulb neck insures a firmly mounted base at all times, and positively prevents any possibility of the base becoming loose or wabbly on the bulb neck.

Further features and advantages of my invention will appear from the following description of a species thereof and from the accompanying drawing, in which Fig. 1 is an elevation, partly in section, of an electric incandescent lamp provided with a seal structure and a mechanical base comprisingmy invention; Fig. 2 is a fragmentary view taken at right angles to Fig. 1, with a portion of the base broken away; Fig. 3 is a view, similar to Fig. 2, showing the base in position onthe bulb neck preparatory toits'application thereto, and Fig. 4 is an elevation, partly in section, of the base and seal portion of a modi vflcation employing a cemented base.

Referring to Fig. 1, the lamp there shown is with a metallic coating ll constituting a reflecting surface. The reflector section II is formed at its vertex with a relatively heavy annular neck or shoulder portion 15 having a flat end wall l6. As shown in Figs. 2 and 3, the outer surface ll of the neck 5| is formed with a reduced diameter portion It to thereby provide an annular abutment shoulder IS. The reduced diameter portion con- I8 is formed with a slight taper and is provided with a pair of diametrically opposite indentations or depressions 20 adjacent the shoulder l9.

-These indentations are preferably spherical or dish-shaped, and are relatively shallow. A filament 2| is mounted within the bulb III, in the desired location therein, by means of flexible leading-in wires 22, 23 hermetically united, preferably by brazing, to metal cups 24, 24 having their edges or rims fused to and sunk and embedded in the thickness of the glass end wall 16. The said cups or skirts 24 may be made of an iron-nickel-cobalt alloy known as Fernico.

I Secured to the neck [5 of the bulb I0 is a base 25 comprising a threaded metallic shell 26, insulation 21, and a metallic center-contact eyelet 28. Leading-in wire 22 is connected to the,

shell'26 while leading-in wire 23 is connected to the eyelet 28. The base is provided with an annular metallic skirt 29 having an inwardly extending flange 30 embedded in the .insulation 21.

In the mechanical form of base shown in Figs.

1-3, the skirt 29 is mounted on the tapered neck portion l8 of the bulb by a press fit, as shown particularly in Fig. 2, with the rim 3| of the" skirt engaging'the abutment shoulder I9 on the bulb. To provide a positive interlock between the base and bulb neck, the skirt 29, after its application to the bulb neck, is formed with a pair of inwardly extending projections or lobes 32 extending into and firmly engaging the surfaces of the indentations 20 in-the bulb neck.

To form the press fit between the base and the bulb, the skirt 29 is made with an inner diameter intermediate the diameter of the outer and inner ends of the tapered neck portion 18 so that when the skirt is initially placed over the tapered neck, it will fit the same in the manner indicated in Fig. 3. The skirt is then forced down onto the tapered heavy neck portion l8 until the rim 3| of the skirt abuts against the annular abutment shoulder I9 on the bulb, as shown in Fig. 2. The resulting press fit, together with the engagement of the rim 3-! with the abutment shoulder;

19, combine to positively eliminate all looseness of the base on the bulb so that there is no possibility of the base becoming wabbly or free to rock. Where the skirt 29 is made of relatively thick metal, or the inner diameter of the skirt is of such small dimensions that the pressure ex-- erted on the bulb neck I8 is apt to be excessive, it may be necessary to longitudinally slit the skirt, at two or more spaced points around its periphery, for a short distance from its rim 3|.

I In this manner the excessive pressure which would otherwise be exerted by the skirt 29 on the bulb neck l3 and which might result in cracking of the same, may be reduced to a comparativelysafe value while still maintaining a suflicient press fit between the said skirt andbulb neck to perform the functions specified. hereinbefore.

After the base has been pressed onto the bulb neck, the metal of the skirt 29 opposite the sphervide suitable holding means for preventing removal of the basefrom the bulb or relative rotational displacement therebetween. The projections 32 on the base extending into the indentations Won the bulb neck therefore merely serve to lock the base in place on the bulb neck, keeping it against the abutment shoulder I 9 on the bulb and preventing relative rotational displacement.

In the modification shown in Fig. 4, the skirt portion 29 of the base 25 abuts against the annular shoulder [9 which serves to center the base on the bulb neck. The said bulb neck is reduced in diameter at 33 to provide space for an annular ring of cement 34 which unites the said base to the bulb neck.

While I have shown and described a preferred embodiment of the invention, it is obvious that various modifications are possible within the scope of the invention. Thus, in the case of the mechanical base structure of Figs. 1-3, while I prefer to employ only two interlocking projec-- tions 32 and, indentations 20 on the base and bulb neck respectively, any desired number may be employed. Furthermore, instead of employing spherical projections 32 and indentations 23, they may be made of any suitable shape or form' to answer the purpose. If desired, the base shell 26 andskirt 29 may be made in one piece, in-

enter and firmly engage the surfaces of said indentations.

2. An electrical device comprising abulb hawing a relatively heavy pressed glass neck portion, and a base comprising a metal shell portion shaped to engage with a socket and a separate metal skirt portion surrounding said bulb neck portion and secured thereon by a press fit, said neck portion being provided with at least one indentation therein and said base being formed with a co-operating protuberance insaid skirt fitting firmly within said indentation.

3. An electrical device comprising a bulb having a. relatively heavy glass neck portion and end wall, said end wall having openings therethrough, an electric energy translation element in said bulb, flexible lead wires extending from said translation element exteriorly of said bulb through the said openings in said end wall, cuplike metallic members having their edges fused to said end wall around the said openings therein to hermetically seal said openings, said lead wires extending through said cup-like members and being hermetically sealed thereto, and. a

base carrying contacts and comprising a shellment in said bulb, flexible lead wires extending from said translation element exteriorly of. said bulb through the said openings in said end wall, cup-like metallic members having theiredges 2,269,620 fused to-said'end wall around the said openings therein to hermetically seal said openi fl. said lead wires extending through said cup-like members and being hermetically sealed thereto, and

a base carrying contacts and comprising a shell said bulb neck portion and portion surrounding a press fit, said bulb neck secured thereon by 

